Washington County’s unemployment rate in May was less than the previous month, and the lowest yet of 2010. The Iowa Workforce Development Office says only 600 members or 5.2% of the Washington County’s workforce was unemployed last month, a 1.6% drop from January, which had the highest jobless rate so far this year.  Iowa’s unemployment rate for May was 6.8%, below the national average of 9.7.  Unemployment also fell in May for Johnson, Keokuk, Henry, Louisa, Jefferson, and Iowa Counties.  Johnson had the lowest unemployment with 4.3%, while Henry had the highest in May with 9%.